Encoding conversation UTF-8 to 1251 in javascript

Question

I need to convert string in UTF-8 to byte array in 1251 codepage in JavaScript. Google says nothing useful. Help :)

EDIT: What is it for.

We have server and client. Server has userpasswords hased with SHA512 and 1251 codepage. Client (web browser) has to hash passwords (provided by user in plain text) with SHA512 and transmit it to the server. The problem is: browser works in UTF-8 encoding, and of course SHA512 in UFT-8 is not the same as SHA512 in 1251. Any Ideas?

EDIT2: got it! :)

    //utf8 to 1251 converter (1 byte format, RU/EN support only + any other symbols) by drgluck
    function utf8_decode (aa) {
        var bb = '', c = 0;
        for (var i = 0; i < aa.length; i++) {
            c = aa.charCodeAt(i);
            if (c > 127) {
                if (c > 1024) {
                    if (c == 1025) {
                        c = 1016;
                    } else if (c == 1105) {
                        c = 1032;
                    }
                    bb += String.fromCharCode(c - 848);
                }
            } else {
                bb += aa.charAt(i);
            }
        }
        return bb;
    } 

Usage with SHA512 implementation by Paul Johnston (http://pajhome.org.uk/crypt/md5/sha512.html)

...
return rstr2hex(rstr_sha512(utf8_decode(input)));

Answer 1

When you access string in javascript, its not even UTF-8 encoding anymore (browsers automatically decode it to built-in javascript encoding OR the one you specified when you load javascript or text, OR default browser encoding), so you need to convert it to UTF-8 first and then convert to cp1251.

Take a look at this unicode encoding converter, I hope you'll get some ideas from that.

Answer 2

This encodes the Unicode codepoints in JavaScript to windows-1251:

var DMap = {0: 0, 1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6, 7: 7, 8: 8, 9: 9, 10: 10, 11: 11, 12: 12, 13: 13, 14: 14, 15: 15, 16: 16, 17: 17, 18: 18, 19: 19, 20: 20, 21: 21, 22: 22, 23: 23, 24: 24, 25: 25, 26: 26, 27: 27, 28: 28, 29: 29, 30: 30, 31: 31, 32: 32, 33: 33, 34: 34, 35: 35, 36: 36, 37: 37, 38: 38, 39: 39, 40: 40, 41: 41, 42: 42, 43: 43, 44: 44, 45: 45, 46: 46, 47: 47, 48: 48, 49: 49, 50: 50, 51: 51, 52: 52, 53: 53, 54: 54, 55: 55, 56: 56, 57: 57, 58: 58, 59: 59, 60: 60, 61: 61, 62: 62, 63: 63, 64: 64, 65: 65, 66: 66, 67: 67, 68: 68, 69: 69, 70: 70, 71: 71, 72: 72, 73: 73, 74: 74, 75: 75, 76: 76, 77: 77, 78: 78, 79: 79, 80: 80, 81: 81, 82: 82, 83: 83, 84: 84, 85: 85, 86: 86, 87: 87, 88: 88, 89: 89, 90: 90, 91: 91, 92: 92, 93: 93, 94: 94, 95: 95, 96: 96, 97: 97, 98: 98, 99: 99, 100: 100, 101: 101, 102: 102, 103: 103, 104: 104, 105: 105, 106: 106, 107: 107, 108: 108, 109: 109, 110: 110, 111: 111, 112: 112, 113: 113, 114: 114, 115: 115, 116: 116, 117: 117, 118: 118, 119: 119, 120: 120, 121: 121, 122: 122, 123: 123, 124: 124, 125: 125, 126: 126, 127: 127, 1027: 129, 8225: 135, 1046: 198, 8222: 132, 1047: 199, 1168: 165, 1048: 200, 1113: 154, 1049: 201, 1045: 197, 1050: 202, 1028: 170, 160: 160, 1040: 192, 1051: 203, 164: 164, 166: 166, 167: 167, 169: 169, 171: 171, 172: 172, 173: 173, 174: 174, 1053: 205, 176: 176, 177: 177, 1114: 156, 181: 181, 182: 182, 183: 183, 8221: 148, 187: 187, 1029: 189, 1056: 208, 1057: 209, 1058: 210, 8364: 136, 1112: 188, 1115: 158, 1059: 211, 1060: 212, 1030: 178, 1061: 213, 1062: 214, 1063: 215, 1116: 157, 1064: 216, 1065: 217, 1031: 175, 1066: 218, 1067: 219, 1068: 220, 1069: 221, 1070: 222, 1032: 163, 8226: 149, 1071: 223, 1072: 224, 8482: 153, 1073: 225, 8240: 137, 1118: 162, 1074: 226, 1110: 179, 8230: 133, 1075: 227, 1033: 138, 1076: 228, 1077: 229, 8211: 150, 1078: 230, 1119: 159, 1079: 231, 1042: 194, 1080: 232, 1034: 140, 1025: 168, 1081: 233, 1082: 234, 8212: 151, 1083: 235, 1169: 180, 1084: 236, 1052: 204, 1085: 237, 1035: 142, 1086: 238, 1087: 239, 1088: 240, 1089: 241, 1090: 242, 1036: 141, 1041: 193, 1091: 243, 1092: 244, 8224: 134, 1093: 245, 8470: 185, 1094: 246, 1054: 206, 1095: 247, 1096: 248, 8249: 139, 1097: 249, 1098: 250, 1044: 196, 1099: 251, 1111: 191, 1055: 207, 1100: 252, 1038: 161, 8220: 147, 1101: 253, 8250: 155, 1102: 254, 8216: 145, 1103: 255, 1043: 195, 1105: 184, 1039: 143, 1026: 128, 1106: 144, 8218: 130, 1107: 131, 8217: 146, 1108: 186, 1109: 190}

function UnicodeToWin1251(s) {
    var L = []
    for (var i=0; i<s.length; i++) {
        var ord = s.charCodeAt(i)
        if (!(ord in DMap))
            throw "Character "+s.charAt(i)+" isn't supported by win1251!"
        L.push(String.fromCharCode(DMap[ord]))
    }
    return L.join('')
}

JavaScript stores each character as raw Unicode codepoints, so the above should work before getting the hash using SHA512.